Rapid growth of information communicating apparatuses, such as a PDA (Personal Digital Assistant), demands higher integration, faster speed, and lower power consumption for memory elements and logic elements available for constituting these communicating apparatuses. In particular, realization of higher density and greater capacity of non-volatile memories has become a more important issue for the art of replacing such a hard disk or an optical disk which is difficult to be down-sized due to presence of moving elements.
Current non-volatile memories include flash memory, which is based on semiconductor technology and FRAM (Ferro-electric Random Access Memory), which is based on a ferro-dielectric technology. Nevertheless, flash memory is problematic in the sense that the writing speed remains on the order of micro-seconds and the re-write cycles are limited. FRAM is problematic in the sense that it is difficult to scale to ultra-high density and the re-writable cycles are insufficient.
A magnetic random access memory (MRAM), on the other hand, is a non-volatile memory that is free from the above-described problems. Due to improvement in physical characteristics of TMR (Tunnel Magneto-Resistive) materials in recent years, MRAM has drawn much attention in this field.
Because of its simple constitution, MRAM can readily be formed into highly integrated configurations. Inasmuch as MRAM executes a write operation by rotation of a magnetic moment, it is possible to secure sufficient re-writable cycles. Further, it is expected that the MRAM can execute accessing operations at an extremely high-speed (e.g. on the order of nano-seconds).
Conventional MRAM manufacturing methods typically do not utilize a lift-off technique. However, this technique is used in manufacture of abutted-junction magnetoresistive recording heads for hard disk drives. Using photo-resist for a mask material in forming elements, this method uses a single masking step to pattern one material by an etching process and a second material by a subsequent deposition and lift-off process. The resulting structure has a region of contact between the etched and lifted films defined by the boundary of the photoresist mask.
This implementation creates a contact region between two films in the same plane. However, for many device applications it is desired to produce a contact region between films on different planes. In particular, it is desirable that the contact does not introduce an electrical short circuit across the device being contacted.
Accordingly, what is needed is method and system for forming a contact in a thin-film device that is capable of minimizes the potential shorting of the device. The method and system should be simple, inexpensive and capable of being easily adapted to existing technology. The present invention addresses this need.